This was a great exploit shared by auverin007, and his thread is Stickied.
HOWEVER i found an improved version of this exploit
1. Run a Heroic Dungeon and complete it
2. when "Choose a Treasure" window is prompted, Quit the dungeon
3. Still receive the Hero Coin after quiting the dungeon
The BEST PART about this method and the DIFFERENCE between the quoted exploit is that the dungeon run does not count as "Completed," so you may repeat the procedure from step 1 for all 16 cycles.
So in Theory, if you do this for every cycle, you can get 32 coins per day
+16 coins from Hell's Furnace
+16 coins from Shrine of Destruction
ps. Currently, this is only confirmed for Nagc only.